My own experience was with its bigger brother, the Stereo 70.
I too found it difficult to achieve the correct bias with pot-travel left.
I had to replace 'short-circuit' output devices in one channel (amplifier/set purchased by me as a duffer), which is why mine blew fuses, everything else seemed ok, aside from the PCB edge connectors & chassis-mount sockets, which were cleaned.
Long story shortened, the 2x diodes connected in series used as thermal monitoring of the output stage? One was leaky ...
12 years later, it's been a great amp with it's life-long partner, the Stereofetic & huge Leak floorstanders, of which, the wife does not approve
Mark